In less than a century

Up to now it was thought that the atmospheric concentration of greenhouse gases should not exceed 450-500 parts per million (ppm) carbon dioxide equivalent (CO2eq), including 360-400 ppm carbon dioxide (CO2). That is double the concentration that existed before the industrial revolution. But studying ice-sheet formation has led James (...)

(1) Carbon dioxide is the main anthropogenic greenhouse gas. Its concentration is expressed in parts per million (ppmCO2). Confusingly, the concentration of other greenhouse gases is expressed in parts per million CO2 equivalent (ppmCO2eq).